Spine pain and joint pain are among the most common worldwide ailments and directly contributes to disability as well as increased duration of care. Spine and joint pain affect work sick leave, production and increased financial costs to healthcare. Non-invasive treatments for spine and joint pain can vary widely from lifestyle changes, physical therapy, oral medication, and select medical devices, that can improve pain level and help improve the quality of life of individuals. Thus, the general population suffers from an ailment that has multiple conservative treatment options with variable outcomes.

Transcutaneous Electrical Neuromuscular Stimulation (TENS) has been show to decrease pain and restore function. Interferential therapy (INF) is a specific signal type that is effective for reducing musculoskeletal pain. Neuromuscular Electrical Stimulation (NMES) uses a specific signal type to cause muscles to contract and therefore provide functional improvement. The RS-4i Plus is an FDA-regulated prescription TENS medical device that outputs an INF signal and a NMES signal, and a unique Intersperse signal, which combines NMES and INF into a single treatment. Therefore, the goal of this study is to determine if use of the prescribed RS-4i Plus in patients presenting with pain, axial or peripheral joint, can be efficacious in decreasing the patient's pain and improving their activity measured at one month, three months, and six months of use.

Inclusion Criteria:

1. chronic and persistent MSK lumbar back pain for greater than 12 weeks as documented in patient records
2. Age 18 to 89
3. Willingness to comply with study protocol
4. Signed Patient Consent on file
5. Verified patient usage collected from RS-4i Plus via patient data adapter

Exclusion Criteria:

1. Pregnancy
2. Any contraindications, as indicated in the RS-4i Plus prescribing information
3. Substantial allergy to adhesives
4. Skin infection or irritation of skin where electrodes are to be placed
5. Pacemaker/ICD
6. Abnormal skin sensation
7. Serious psychological disorder
8. End-stage cardiac, peripheral arterial or pulmonary disease
9. h/o recent vertebral fracture
10. Severe degenerative or traumatic neuromuscular disease
11. Non-English speaking
12. Uncontrolled diabetes meelitus (Hb A1c> 8.5%)
13. ESRD or ESHD
14. Active cancer

Subjects will be current adult patients of the UCI PM&R or Orthopedic Department